I recently purchased a 12 string acoustic. I noticed that playing certain chords at the nut end sounded out of tune, also it appeared to be difficult to hold down certain chords.

I noticed that the strings were set-up quite high on the nut, particularly the B strings. So I removed it and applied some sandpaper to the base of it, thus lowering the strings to the Neck.  The reason it was sounding out of tune is because of the height between where the strings sit on the nut and the first fret, if I played a C chord, the  B strings would need to bend in order to play a note, thus putting it out of tune, plus making it harder work to get a clean striking chord.

If you are going to attempt to do this, sand a little bit at a time, refit and check the heights, it's amazing you only have to shave off a little bit. Also, as the B string groove was set higher than the other strings, I filed it down to match the other grooves.

The result was amazing, not only does the guitar sound in tune, it's much easier to play, you don't need to apply as much pressure with your chord fingers, thus you are more relaxed, better feel.

This guitar only cost me £85.00, it now sounds like a high quality acoustic guitar

+1 on this.. I do this to all my guitars. Proper set up makes life so much easier.

awesome tip denis...ill have to try this on my 6 string acoustic as its sounding "out of tune" and whatnot like you described. thanks man!

Go aasy on the sanding, When I did it  I just loostened the strings enough so that I could check the level a bit at a time.

ill be very sparing on the sanding. thanks man!